KR101290125B1 - Glass composite for aspheric lens - Google Patents

Abstract

The present invention relates to a glass composition for an aspherical lens, and according to the present invention, for an aspherical lens having a high Abbe's number while having a high refractive index of 1.58 or more by appropriate combination of SiO ₂ , B ₂ O ₃ , Li ₂ O and BaO. It is possible to provide optical glass.

Description

Glass composition for aspherical lens {Glass composite for aspheric lens}

The present invention relates to a glass composition for an aspherical lens, and more particularly, to a glass composition for an aspherical lens having a SiO ₂ -B ₂ O ₃ -BaO-Li ₂ O system as a main component and having a high refractive index and Abbe's number. will be.

Since 2005, the average annual growth rate of mobile phones is expected to be 8%. Along with the convergence of mobile devices, the aspheric lens market is growing along with the growth of the camera market. Due to the auto focusing and thinning of cameras for mobile devices, the number of lenses required is decreasing, and spherical lenses made of plastic are difficult to meet the needs of thin products.

The reason for this phenomenon is due to the difference in the structure of the spherical lens and the aspherical lens. 1 is a photograph showing the refraction and convergence of parallel rays when taken with a spherical lens (a) and an aspherical lens (b).

Referring to FIG. 1, in the case of the spherical lens a, it is difficult for the parallel lights to converge at one point because there is a difference in refractive index depending on the point of incidence of the parallel light. However, in the case of the aspherical lens (b), even if the incidence point of the parallel light is different, the parallel light is configured to be collected at one point by adjusting the refraction of the light.

As a result, as shown in FIG. 1, in the case of the aspherical lens b, the image is clearly seen as compared with the spherical lens a.

In addition, in the case of the spherical lens (a), it is inevitable to form a lens by combining a plurality of spherical lenses (a). Accordingly, the accuracy of the lens arrangement is required. In addition, the combination of the spherical lens a occupies a relatively large volume and a large weight. And it is difficult to provide high optical performance.

On the other hand, since the aspherical lens (b) can make parallel light gather at a point, an error due to chromatic aberration of light can be minimized. As compared with the spherical lens a, the number of lenses is greatly reduced. And it is possible to provide high optical performance.

In particular, demand for aspherical glass lenses is skyrocketing due to the emergence of high-resolution / high-performance camera phones and global competitiveness in the laser printing market. Currently, the 2 mega zoom lens of the camera phone is using 2G (glass) + 2P (plastic) or 1G + 3P type, but due to the size of the camera, it is necessary to use aspherical glass lens.

The purpose of the use of aspherical lens is to reduce the chromatic aberration, to improve the image quality and to shorten the overall length so that a slimmer product is possible.

However, although the demand for aspherical glass lenses is increasing in this way, the base material is mostly dependent on imports. Although the necessity of domestic cameras, printers and various aspherical glass lenses is gradually increasing, all glass base materials for aspherical lenses, which are basic materials, are imported. Representative sources include Ohara, Hoya, Sumita, and NEG. Recently, the market for camera module for rearview sensor has expanded, and the demand for aspherical glass lens is exploding.

In keeping with this tendency, research and development on aspherical lenses is continued, but aspherical lenses with high refractive index and high Abbe's number have not been developed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a glass composition for an aspherical lens having a SiO ₂ -B ₂ O ₃ -BaO-Li ₂ O-based composition and having a high refractive index and Abbe number.

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The present invention is a glass composition for an aspherical lens in which parallel light is collected at one point, 45 to 57 mol% SiO ₂ , 1 to 5 mol% Na ₂ O. Provides a glass composition for an aspherical lens consisting of optical glass comprising B ₂ O ₃ 3-12 mol%, Li ₂ O 21-32 mol%, BaO 5-15 mol%, Al ₂ O ₃ 0.5-5 mol%. .

The glass composition may further contain 0.01 to 2 mol% K ₂ O.

It is preferable that the glass composition has a refractive index of 1.565 to 1.610.

The glass composition preferably has Abbe number (V) of 57 to 60.

The glass composition is preferably a glass transition temperature (Tg) of 400 ~ 470 ℃.

The glass composition is preferably an expansion softening point (T _dsp ) of 470 ~ 510 ℃.

The glass composition preferably has a coefficient of thermal expansion (CTE) of 90 to 110 × 10 ⁻⁷ / ° C.

(a) SiO ₂ 45 ~ 57 mol%, Na ₂ O 1 ~ 5 mol%. 3 to 12 mol% of B ₂ O ₃ , 21 to 32 mol% of Li ₂ O, 5 to 15 mol% of BaO, and 0.5 to 5 mol% of Al ₂ O ₃ , and (b) the mixed raw powder An aspheric lens comprising melting and homogenizing the same, (c) shaping and cooling the molten homogenized glass, and (d) cutting, coring, and lapping the cooled and formed glass composition. It provides a method for producing optical glass for use.

In the step (a), it is preferable to further mix 0.01-2 mol% K ₂ O.

Melting and homogenizing the mixed raw material powder in step (b) further includes clarifying and stirring, wherein the melting may be performed at a temperature of 1350 to 1500 ° C.

According to the glass composition for the aspherical lens and the method for manufacturing the optical glass for the aspherical lens using the same, according to the present invention, SiO ₂ , B ₂ O ₃ , BaO and Li ₂ O with a high refractive index while maintaining a high refractive index It is possible to provide optical glass for aspherical lenses.

1 is a photograph showing the refraction and convergence of parallel rays when taken with a spherical lens (a) and an aspherical lens (b).
2A to 2C are graphs showing the effect of SiO ₂ , BaO, and Li ₂ O on Abbe's number.
3A to 3C are graphs showing the effects of SiO ₂ , BaO, and Li ₂ O on n _D.
4A to 4C are graphs showing the effect of SiO ₂ , BaO and Li ₂ O on n _F.
5A to 5C are graphs showing the effect of SiO ₂ , BaO, and Li ₂ O on n _C.
6A to 6C are graphs showing the effects of SiO ₂ , BaO and Li ₂ O on the glass transition temperature (T _g ).
7A to 7C are graphs showing the effect of SiO ₂ , BaO and Li ₂ O on the expansion softening point (T _dsp ).
8A to 8C are graphs showing the effects of SiO ₂ , BaO, and Li ₂ O on the coefficient of thermal expansion (CTE).
9A to 9C are graphs summarizing main effects and interactions according to SiO ₂ , BaO, and Li ₂ O on the glass transition temperature (T _g ).
10a to 10c are graphs summarizing the main effects and interactions according to SiO ₂ , BaO and Li ₂ O on the coefficient of thermal expansion.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not. Wherein like reference numerals refer to like elements throughout.

The raw materials are weighed and mixed to form a glass composition for an aspherical lens. In the glass composition for the aspherical lens according to the present invention, SiO ₂ , B ₂ O ₃ , BaO, Li ₂ O, Na ₂ O and Al ₂ O ₃ may be used as the raw material powder. In addition, K ₂ O may be further included as the raw material powder. The raw powder is mixed according to the batches of SiO ₂ , B ₂ O ₃ , B ₂ O ₃ , BaO, Li ₂ O, Na ₂ O, Al ₂ O ₃ and K ₂ O which are the raw materials of the glass composition.

SiO ₂ is an oxide that forms glass and is an essential component for forming a skeleton of glass. In addition, SiO ₂ is easy to control the viscosity of the glass by adjusting its content, and is an effective ingredient for improving the resistance to devitrification. If the content of SiO ₂ is too small, the devitrification resistance may worsen, and the refractive index may be low. Therefore, the content of SiO ₂ is preferably 45 mol% or more. In addition, the content of SiO ₂ is preferably 57 mol% or less. If the content of SiO ₂ is too high, the glass transition temperature (T _g ) or the viscosity of the glass tends to be high, and undissolved products are likely to occur.

B ₂ O ₃ is a glass forming oxide component. If the content of B ₂ O ₃ is not sufficient, it is difficult to form a glass having a high refractive index. If the content of B ₂ O ₃ is excessive, it is difficult to maintain the glass transition temperature (T _g ) below 470 ° C. In consideration of this, the amount of B ₂ O ₃ is preferably 3 to 12 mol%.

BaO serves to increase the refractive index of the glass while improving meltability. When the content of BaO is too high, the devitrification resistance tends to be weakened, so the content of BaO is preferably 15 mol% or less. In addition, in order to secure the refractive index of the glass, the content of BaO is preferably 5 mol% or more.

Li ₂ O is a very effective component to lower the devitrification temperature and the glass transition temperature. Li ₂ O is also effective in lowering the specific gravity together with SiO ₂ and B ₂ O ₃ . If the content of Li ₂ O is not sufficient, the effect of lowering the devitrification temperature and the glass transition temperature is insufficient. If the amount of Li ₂ O is excessive, the devitrification temperature may not be lowered and the glass transition temperature T _g may increase. Therefore, the content of Li ₂ O is preferably in the range of 21 to 32 mol%.

Na ₂ O lowers the glass transition temperature (T _g ) and is an effective component for improving meltability. Too much Na ₂ O content may impair devitrification and chemical durability, and Na ₂ O is preferably contained in an amount of 1 to 5 mol%.

In the present invention, the vitrification process is performed on the raw material in powder form for melting the glass raw material. At this time, Li ₂ O has the effect of lowering the glass transition temperature (T _g ) and promoting the melting of the glass raw material. However, the components of such a Li ₂ O is too large, it can degrade the stability of the glass and, lowering the mechanical strength.

Al ₂ O ₃ serves to improve the devitrification resistance and chemical durability of the glass. When the content of Al ₂ O ₃ is too high, vitrification becomes difficult, and the glass transition temperature T _g may increase. Therefore, the content of Al ₂ O ₃ is preferably 0.5 to 5 mol%.

K ₂ O lowers the glass transition temperature and improves meltability. If the content of K ₂ O is too high, devitrification resistance and chemical durability may worsen. Therefore, the content of K ₂ O is preferably in the range of 0.01 to 2 mol%.

The weight ratio with respect to each of these components, the influence on the refractive index, Abbe's number of glass, etc. are mentioned later.

The raw material powder of glass is weighed according to the designed compounding ratio. And the raw material powder of the weighed glass is mixed in order to improve the dispersibility with respect to a glass component. In the case of the glass composition for the aspherical lens, if it is not uniformly mixed, the refractive index and the optical constants such as Abbe's number are partially different, which results in deterioration of physical properties.

For this homogenization, it is necessary to use a stirring apparatus suitable for the viscosity of the glass and the viscosity of the glass. Therefore, in consideration of the viscosity of the glass at 1350 ~ 1500 ℃ when melting the stirrer (stirrer) to 20rpm and 50rpm stirring experiment was performed. As a result, in the case of 20rpm, the degree of mixing evenly appeared less, but in the case of 50rpm, it was confirmed that the mixing evenly.

In order to ensure homogeneity after molding and melting of the glass composition for an aspherical lens, a three-dimensional turbulent mixer is used in the present invention. Three-dimensional turbulent mixer is a device that can maximize the mixing state of the raw powder than the simple horizontal mill by moving the container in the three-axis direction. Therefore, in the present invention, it is preferable to overcome the nonuniformity inside the glass by mixing at 10 ~ 50rpm for 30 minutes to 24 hours using a device such as a three-dimensional turbulent mixer.

In particular, when a small amount of added ingredients are not evenly mixed, the influence on the physical properties of the optical glass is enormous. After mixing the raw powders in this way, melting and homogenizing operations are necessary to obtain a glass composition. This melting operation is preferably carried out in a melting furnace or crucible of platinum (Pt) material. It is preferable that the said melting is made at 1350-1500 degreeC.

In the melting process, a non-uniform material remains during incomplete melting, and the residual of such non-uniform material is an obstacle to the performance expression of the glass composition for the aspherical lens. In order to prevent such obstacles, a refining process is performed. This clarification process is a process for removing the bubble which generate | occur | produced at the time of melting of a glass raw material. Then, a sterling operation is performed as a process for homogenizing the glass composition. Striae is generated inside the aspherical lens due to the specific gravity difference of the glass raw material, and the phenomenon of the stria can be suppressed by making the glass composition uniform.

Then, the molten and homogenized product is poured into a mold, and the molding and cooling are performed. The reason for proceeding with slow cooling is to avoid birefringence by removing residual stress and to secure a stable position of the atomic structure during the cooling process.

When the molding and slow cooling process is completed, the glass composition becomes a glass mass, and the glass mass is processed to produce optical glass. The machining process may consist of coring and lapping. The coring process is a process of cutting the slow cooled agglomerated glass and producing a glass of a desired shape. It can be processed into ball lens shape and rod shape. When the coring is completed, lapping is performed on the glass.

Hereinafter, embodiments of the glass composition for the aspherical lens according to the present invention will be described in more detail, and the present invention is not limited to the following examples.

≪ Example 1 >

It was weighed to be 51 mol% SiO ₂ , 8 mol% B ₂ O ₃ , 10.5 mol% BaO, 25 mol% Li ₂ O, 3 mol% Na ₂ O and 2.5 mol% Al ₂ O ₃ . Each weighed component was mixed for 20 minutes at 50 rpm using a three-dimensional turbulent mixer.

In the case of the present invention, since the influence of the mixing process of the raw material powder contained in the glass liquid is important, a three-dimensional turbulent mixer was used to evenly mix the portion where the trace amount of the oxide raw material is added.

By using a three-dimensional turbulent mixer, it is possible to suppress partial melting in a subsequent glass melting process and to obtain a glass composition for aspherical lenses having an even distribution.

Melting was performed on the raw powders thus mixed. The melting was carried out at 1450 ° C. for 3 hours with the raw powder mixed in a platinum (Pt) crucible. Refining was performed on the glass formed through this melting process. After clarification was completed, a stirring operation was performed to homogenize. As described above, the stirling operation is to suppress generation of stria in the optical glass for aspherical lens. Sterling results were subjected to slow cooling.

A specimen for measuring the dilometer was made on the glass composition thus formed, and a specimen for measuring the refractive index was prepared.

For the measurement of the dilatometer, a molded body having a length of 20 mm and a diameter of 5 mm was manufactured, and a rectangular parallelepiped having a width and length of 15 mm was required for measuring the refractive index.

The physical properties of the glass compositions made to meet the specifications were measured and reflected in the design according to the Design of Experiment (DOE).

<Example 2>

Weighed to be 51 mol% SiO ₂ , 8 mol% B ₂ O ₃ , BaO 10.5 mol%, Li ₂ O 25 mol%, Na ₂ O 3 mol%, Al ₂ O ₃ 2.0 mol% and K ₂ O 0.5 mol% It was. Each weighed component was mixed for 1 hour at 50 rpm using a three-dimensional turbulent mixer.

The following process was carried out in the same manner as described in Example 1 to prepare a glass composition.

Thus prepared glass compositions were prepared for the measurement of the coefficient of thermal expansion and the refractive index in order to observe the optical and physical properties.

A sample having a length of 20 mm and a diameter of 5 mm was prepared for measuring the coefficient of thermal expansion with a dilatometer. Samples of cuboids having a length of 15 mm and a length of 15 mm were prepared for the measurement of the refractive index.

Various physical properties, refractive index, Abbe's number, expansion softening point (T _dsp ), thermal expansion coefficient (CTE), and residual stress (birefringence) of the samples prepared as described above were measured.

Refractive index is measured separately n _D , n _F , n _C. n _D is a refractive index at 587.6 nm, n _F is a refractive index at 486.3 nm, and n _C is a refractive index at 656.3 nm.

As an evaluation index of the glass composition according to the present invention, Abbe's number, refractive index, expansion softening point (T _dsp ), glass transition temperature (T _g ), and coefficient of thermal expansion (CTE) were used.

Abbe's number shows the dispersion degree of the refractive index of an optical glass material, As shown by Formula (1), when the refractive index for each wavelength is mutually compared and the value is large, dispersion is small, and when the value is small, dispersion is large. The large dispersion means that the glass is a material having a large change in refractive index with wavelength and a large influence of chromatic aberration.

Fraun Hopper found that there are many black lines besides seven different colors from the sun's light, and Fraun Hopper examined the sun's spectrum in detail and found 324 black lines, which are called Fraun Hopper lines or absorption lines. .

Fraun hoppers are created by the absorption of some of the light into a substance. Atoms, ions, and molecules only absorb light of a specific wavelength, so irradiation of absorption lines provides information on the type and amount of elements present and the temperature, density, motion, and magnetic field strength of the environment in which these elements are located. The number of Fraun Hopper ships known to date is over 30,000, and these Fraun Hopper ships in the solar spectrum are evidence of light-absorbing material between the Earth and the Sun. The intensity or width of the spectrum is also a clue to the number of atoms that emit or absorb light and the state of motion.

If the refractive index of the Fraun hopper line with respect to the F and C lines is n _F , n _C and the refractive index of the D line is n _D , Abbe's number v is expressed by Equation 1 below.

The characteristics of the material with high dispersion mean that the color dispersion by the prism is large. The spectrum spreads from red to purple is long.

Table 1 summarizes the experimental results performed according to the first experimental design.

Furtherance SiO ₂
(mole%) BaO
(mole%) Li ₂ O
(Mol%) Abbe's (v) n _F n _D n _C CTE
(10 ^-7 / ℃) T _g (° C) T _dsp (℃)
One 48 8 22 58.76 1.5900 1.5752 1.5724 129 458.90 494.25
2 54 8 22 59.78 1.5898 1.5696 1.5667 122 469.90 508.20
3 48 12 22 55.82 1.5945 1.5873 1.5840 119 456.00 486.95
4 54 12 22 57.67 1.5963 1.5893 1.5861 116 471.40 508.86
5 48 8 28 58.81 1.5843 1.5777 1.5745 125 441.50 471.38
6 54 8 28 59.37 1.5885 1.5817 1.5787 123 453.50 487.10
7 48 12 28 57.37 1.5890 1.5822 1.5789 127 436.10 468.73
8 54 12 28 58.94 1.5918 1.5850 1.5819 126 447.49 479.99
9 51 10 25 57.10 1.5879 1.5808 1.5777 120 451.50 488.62

Referring to Table 1, the predicted values and the measured optical properties were very similar, and the glass transition temperature (T _g ) was similar, but the coefficient of thermal expansion (CTE) and expansion softening point (T _dsp ) showed different results. The expansion softening point (T _dsp ) is a value known to be affected by mechanical errors, and even if ignored, the coefficient of thermal expansion (CTE) was quite different.

Composition 6 showed a value close to the physical property target of the present invention. In particular, the glass transition temperature (T _g ) and expansion softening point (T _dsp ) showed a value lower than 50 ℃ than the physical property target of the present invention. From this, it was judged that it would be very advantageous for the molding operation at low temperature. However, the coefficient of thermal expansion as a whole showed a somewhat higher value than the physical property target of the present invention. If the product is manufactured according to the composition of Table 1 above, it has been developed a material showing excellent characteristics when working at low temperatures, but cracking may occur during the cooling process.

In the present invention, further experiments were conducted to reduce the coefficient of thermal expansion (CTE).

2A to 2C are graphs showing the effect of SiO ₂ , BaO, and Li ₂ O on Abbe's number. 2A is a Pareto chart of standardized effects. Figure 2b shows the variation of Abbe number according to the main components SiO ₂ , BaO and Li ₂ O, Figure 2c shows the effect on the interaction of each component.

2A to 2C, it is determined that SiO ₂ and BaO affect Abbe's number. Of course, according to the analysis according to the main components SiO ₂ , BaO and Li ₂ O of FIG. 2b, it was observed that Li ₂ O also affected, but even in a situation where the effective level of 0.1 is relaxed, Li ₂ O is significant in the pareto of the effect. Depart from the level Since the interaction between the components of FIG. 2C is almost insignificant, when observed with the main effect alone, as the amount of SiO ₂ increases, the Abbe number increases, and BaO has the opposite effect.

3A to 3C, 4A to 4C, and 5A to 5C are graphs showing the effects of SiO ₂ , BaO, and Li ₂ O on n _D , n _F , and n _C , respectively.

3A to 3C are graphs showing the effects of SiO ₂ , BaO, and Li ₂ O on n _D. 3A is a Pareto chart of standardized effects. FIG. 3b shows the variation of n _D according to SiO ₂ , BaO and Li ₂ O as main components, and FIG. 3c shows the effect on the interaction of each component. n _D represents a refractive index at 587.6 nm.

Referring to FIG. 3B, it was determined that BaO was influential in the effective level of 10% in the analysis of the principal component of FIG. 3B with respect to n _D. As BaO increased, the value of n _D increased.

Also in the interaction between the components of Figure 3c BaO and Li ₂ O was shown to increase the n _D.

4A to 4C are graphs showing the effect of SiO ₂ , BaO and Li ₂ O on n _F. 4A is a Pareto chart of standardized effects. Figure 4b shows the variation of n _F according to the main components SiO ₂ , BaO and Li ₂ O, Figure 4c shows the effect on the interaction of each component. n _F represents a refractive index at a wavelength of 486.1 nm.

Referring to FIG. 4B, in the analysis of the principal component of FIG. 4B with respect to n _F , it was determined that BaO was influential in the effective level of 10%. N _F increased with increasing BaO.

Also in the interaction between the components of Figure 4c BaO and Li ₂ O was shown to increase the n _F increased.

5A to 5C are graphs showing the effect of SiO ₂ , BaO, and Li ₂ O on n _C. 5A is a Pareto chart of standardized effects. Figure 5b shows the variation of n _C according to the main components SiO ₂ , BaO and Li ₂ O, Figure 5c shows the effect on the interaction of each component. n _C represents a refractive index at a wavelength of 656.3 nm.

Referring to FIG. 5B, the analysis of the principal component of FIG. 5B for n _C showed that BaO was influential in the range of 10% of the effective level. As BaO increases, n _C increases.

Also in the interaction between the components of Figure 5c BaO and Li ₂ O was shown to increase the n _C.

In terms of the effect on the thermal characteristics, the glass transition temperature (T _g ) and the expansion softening point (T _dsp ) are the ones that most influence the process condition setting. In the case of the glass transition temperature (T _g ), the value increases with increasing content of SiO ₂ , a network former, and decreases with increasing Li ₂ O or BaO, which is a network modifier. The degree of effect was found to be insignificant due to the BaO significantly lower impact.

It is evident that Li ₂ O is the major influence on the glass transition temperature (T _g ). From the relationship with the refractive index, it was confirmed that Li ₂ O had no great effect. Since it has been observed to have an effect of increasing Abbe number, it is expected that an appropriate increase in the amount of Li ₂ O can achieve the desired optical properties while sufficiently reducing the working temperature.

6A to 6C are graphs showing the effects of SiO ₂ , BaO and Li ₂ O on the glass transition temperature (T _g ). 6A is a Pareto chart of standardized effects. Figure 6b shows the change in the glass transition temperature (T _g ) according to the main components SiO ₂ , BaO and Li ₂ O, Figure 6c shows the effect on the interaction of each component.

Referring to FIG. 6A, it was confirmed that Li ₂ O exhibited the greatest influence. When the influence of each component of Figure 6b the more Li ₂ O is increased and drop the glass transition temperature (T _g), if SiO ₂ is increased with increasing the glass transition temperature (T _g).

Also in the interaction between the components of Figure 6c BaO and Li ₂ O was shown to decrease the glass transition temperature (T _g ).

7A to 7C are graphs showing the effects of SiO ₂ , BaO and Li ₂ O on the dilatometric softening point (T _dsp ). 7A is a Pareto chart of standardized effects. Figure 7b shows the change in the expansion softening point (T _dsp ) according to the main components SiO ₂ , BaO and Li ₂ O, Figure 6c shows the effect on the interaction of each component.

Referring to FIG. 7A, it was confirmed that Li ₂ O exhibited the greatest influence. Referring to the influence of each component of FIG. 7B, as the Li ₂ O increases, the expansion softening point (T _dsp ) decreases, and when SiO ₂ increases, the expansion softening point (T _dsp ) increases.

Also in the interaction between the components of Figure 7c BaO and Li ₂ O was shown to decrease the expansion softening point (T _dsp ).

8A to 8C are graphs showing the effects of SiO ₂ , BaO, and Li ₂ O on the coefficient of thermal expansion (CTE). 8A is a Pareto chart of standardized effects. FIG. 8B shows the variation in the coefficient of thermal expansion according to SiO ₂ , BaO and Li ₂ O, which are the main components, and FIG. 8C shows the effect on the interaction of each component.

There was no effective level of component in the coefficient of thermal expansion. However, the main effect of increasing the amount of Li ₂ O was found to increase the coefficient of thermal expansion. In addition, the interaction between Li ₂ O and BaO showed the highest effect. In particular, when BaO is high, the increase of Li ₂ O increases with the coefficient of thermal expansion.

As the network modifier increases, the coefficient of thermal expansion increases. However, when BaO is low, Li ₂ O seems to have an effect of firming the structure somewhat due to the influence of the ionic field strength. However, when BaO was increased, there was no effect of ion field strength of Li ₂ O.

Table 2 shows the results of the second experimental design.

Furtherance BaO
(mole%) SiO ₂
(Mol% ₎ Al ₂ O ₃
(mole%) Li ₂ O
(mole%) CTE
(10 ^-7 / ℃) T _g
(℃ ₎ T _dsp
(℃) Abbe's (v) n _F n _D n _C One 5 48 0 10 88 513 551 * * * * 2 15 48 0 10 94 530 578 * * 1.6089 * 3 5 58 0 10 77 512 549 * * * * 4 15 58 0 10 95 537 577 * * 1.60969 * 5 5 48 5 10 81 522 561 * * 1.57945 * 6 15 48 5 10 94 525 572 * * 1.60955 * 7 5 58 5 10 71 524 568 * * 1.6099 * 8 15 58 5 10 97 574 535 * * 1.60073 * 9 5 48 0 20 108 472 508 * * 1.58235 * 10 15 48 0 20 115 469 503 78.22 1.61454 1.60868 1.60676 11 5 58 0 20 101 482 521 * * 1.56136 * 12 15 58 0 20 108 489 522 * * 1.60162 * 13 5 48 5 20 96 478 510 58.96 1.57144 1.5649 1.56186 14 15 48 5 20 101 473 507 59.38 1.61087 1.60386 1.6007 15 5 58 5 20 88 483 530 * * 1.5964 * 16 15 58 5 20 102 487 526 * * 1.5888 * 17 10 53 2.5 15 103 505 554 59.16 1.588 1.5811 1.5782

Composition No. 17 in Table 2 is an experiment to select the composition most similar to the chemical component analysis results. Since the experimental range was slightly widened, some of the deviations occurred outside the vitrification range, resulting in no refractive index data. Accordingly, the experimental results on the refractive index, which is an optical characteristic value, could not be obtained. However, it is believed that the problem of coefficient of thermal expansion has been solved.

In particular, composition 14 is a very likely composition, and if the BaO content is slightly lowered, it may be applicable to an optical glass having excellent optical and thermal properties.

The transmittance measurement experiments were performed based on the results of the first experimental design and the second experimental design. The transmittance measurement was performed using a Varian Cary 100 model. As a result of the measurement, the glass was very clear and transparent, and the transmittance was 90%.

In addition, since the raw material of the reagent grade was used, the wavelength of the UV-cut was about 300 nm.

9A to 9C are graphs summarizing main effects and interactions according to SiO ₂ , BaO, Li ₂ O, and Al ₂ O ₃ with respect to the glass transition temperature (T _g ). 9A is a Pareto chart of standardized effects. 9b shows the variation in the glass transition temperature according to the main components SiO ₂ , BaO, Li ₂ O and Al ₂ O ₃ , and FIG. 9c shows the effect on the interaction of each component.

Referring to FIG. 9A, except for Li ₂ O, SiO ₂ , BaO, Li ₂ O, and Al ₂ O ₃ were judged to have a small effect on the glass transition temperature. But in the case of Li ₂ O, Li ₂ O is an increase to lower the glass transition temperature (T _g), is increased when the Li ₂ O decreases the glass transition temperature (T _g).

9B, all of SiO ₂ , Al ₂ O ₃ , and BaO had an effect of increasing the glass transition temperature (T _g ).

Referring to FIG. 9C, it was confirmed that BaO and Li ₂ O interacted to affect the glass transition temperature (T _g ). The expansion softening point (T _dsp ) showed a tendency similar to the glass transition temperature.

10A to 10C are graphs summarizing main effects and interactions according to SiO ₂ , BaO, Li ₂ O, and Al ₂ O ₃ on the coefficient of thermal expansion (CTE). 10A is a Pareto chart of standardized effects. FIG. 10B shows the variation in the glass transition temperature (T _g ) according to the main components SiO ₂ , BaO, Li ₂ O and Al ₂ O ₃ , and FIG. 10C shows the effect on the interaction of each component.

Referring to FIG. 10A, it was confirmed that Li ₂ O was the main factor even in experiments mainly in which the coefficient of thermal expansion was based on SiO ₂ , BaO, Li ₂ O, and Al ₂ O ₃ .

In FIG. 10B, it was confirmed that the network former and the network modifier contributed to opposite tendencies. SiO ₂ and Al ₂ O ₃ are the formers, and BaO and Li ₂ O are the modifiers. Li ₂ O and BaO were affected at the significance level of 10%. The coefficient of thermal expansion decreased with increasing SiO ₂ and Al ₂ O ₃ , and the coefficient of thermal expansion increased with increasing Li ₂ O and BaO.

As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment, A various deformation | transformation by a person of ordinary skill in the art within the scope of the technical idea of this invention is carried out. This is possible.

Claims (10)

A glass composition for an aspherical lens where parallel light gathers at one point,
SiO ₂ 45-57 mol%, B ₂ O ₃ 3-12 mol%, BaO 5-15 mol%, Li ₂ O 21-32 mol%, Na ₂ O 1-5 mol%, Al ₂ O ₃ 0.5-5 Mol% and K ₂ O 0.01-2 mol%,
The glass composition,
Glass transition temperature (T _g ) is 400 ~ 470 ℃,
Expansion softening point (T _dsp ) is 470 ~ 510 ℃ higher than the glass transition temperature (T _g ),
A glass composition for an aspherical lens, characterized in that the coefficient of thermal expansion (CTE) is 90 ~ 110 × 10 ^-7 / ℃.
delete The glass composition according to claim 1, wherein the glass composition has a refractive index of 1.565 to 1.610.
The glass composition according to claim 1, wherein the glass composition has Abbe number (V) of 57 to 60. delete delete delete delete delete delete

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